Effects Of Quality For Litopenaeus Vannamei Cultured In Low Salinity Water By Adding Different Salt In Feed

Litopenaeus vannamei was fed with basal diets respectively supplemented with 0%, 1%, 2%, 4% salt in low salinity water for 40 days, in which the effects of muscle quality were measured. The contents of the research are including four parts. (1) Effects of muscle nutritional composition for Litopenaeus vannamei cultured in low salinity water by adding different levels salt in feed. (2) Effects of texture for Litopenaeus vannamei cultured in low salinity water by adding different levels salt in feed. (3) Effects of muscle histology for Litopenaeus vannamei cultured in low salinity water by adding different levels salt in feed. (4) Effects of muscle fatty acid and hepatopancres acid for Litopenaeus vannamei cultured in low salinity water by adding different levels salt in feed.The results are as follows.(1) Common chemical composition, amino of P. vannamei were examined, and sensory analysis were employed to study the effects of four groups of shrimp. The results showed that the content of muscle protein and ash were increased, but the moisture and lipid were decreased. Such as, when the adding level is 4%, the protein content significantly higher than the other group(sP<0.01), while its moisture content was significantly lower than the other three(P<0.05). As the addition of salt increasing, the amino acids of shrimp were increased, and significantly improved in flavor characters, especially for the addition of 4% salt group.(2) The textural characters of raw and cooked Litopenaeus vannamei cultured in low salinity water by adding different levels salt in feed were analysised. The results described that as the addition of salt increasing, the index of texture were increased except adhesiveness no matter raw shrimp or cooked shrimp. The texture measurements gave some different results for raw and cooked shrimp. For the raw ones, hardness, springiness, gumminess, chewiness, resilience were showed no significant difference when adding 1%, 2% salt in feed, but 4% addition showed significantly superior to the other groups(P<0.05). The cohesiveness showed no significant difference(P>0.05). As to the cooked shrimp,the hardness of control group was significantly lower than other group, its adhesiveness was the highest(P<0.05). The springiness and resilience of 4% addition were significantly higher than the other three groups(P<0.05). The rest index showed no difference.Results above showed that the muscle texture of the shrimp could be improved by feeding different levels of salt in low salinity water, and the proper addition was 4%.(3) The histology of the second abdominal flexor muscle on four low water shrimps and one seawater shrimp were observed using light microscope and electron microscope. The results showed that the alignment of the muscle fibre were porosity on the control group and 1% group, some were gatherd cord, some were bent, and the gap of some perimysium were wide. But as the addition of salt increasing, it resulted in some improvement, especially for the 2%, 4% addition, they were well-distributed than the other. The ultrastructure of the shrimp showed that the myofilament arrayed irregular, in-completed in the front two groups, but the 4% addition was much better, which has no difference to seawater one, they all distributed uniformity, and the myofilament arrange in sexangular point. On lonitudined section, the sarcomere on the control group and 1% group were untidy, some are twist and overlapping. The addition of 4% salt group has good-shaped, clear-distinguished, and the length of sarcomere is significantly higher than the other groups(P<0.05). As the addition of salt increasing, myofibril diameter, solid thick filament diameter, hollow thick filament diameter, A band width, H band width show significant difference(P>0.05).(4) The fatty acid composition in muscle and hepatopancres of P. vannamei were analysised. The results showed as follows. In muscle, the main fatty acid type is PUFA, and the content of the PUFA is significantly higher than MUFA, especially for EPA and DHA. No matter lowerwater shrimp or seawater shrimp, the content of EPA and DHA is more than 20%, among those,ω-3 fatty acid accounts more. As the adding of salt increasing, the content of SAFA is decreased, except C14: 0, the other SAFA has no significantly difference between the experimental group(P>0.05). But comparing with other groups, the addition of 4% salt group has the lowest content(P<0.05). The total PUFA, MUFA contents were higher on 4% salt group than the other. C16: 1 is significantly high than the other.When adding 4% salt in feed, C18: 1, C20: 1 are significantly high. In P. vannamei hepatopancres, the contents of C16: 0, C18: 1 are high, but the contents of EPA and DHA were lower comprared with muscle fatty acid. Together with muscle fatty acid, as the addition of salt increasing, the content of UFA, EPA, DHA have a tendency to raise up.